PART VIII — AQUATIC ECOSYSTEMS 



long history of aquaculture in this 

 country to permit estimates of aver- 

 age cost or average profit. 



Current Research Activity 



The larger, more progressive cor- 

 porations are doing more than asking 

 questions of the biologists. They are 

 paying for research on the biological 

 and marketing aspects of aquaculture 

 in order to judge whether their cor- 

 porations should enter into these 

 ventures. 



Despite the lack of economic data 

 to justify large-scale aquaculture in 

 developed countries, many facts and 

 principles gained from biological re- 

 search and from common sense serve 

 as guidelines for anyone interested 

 in fish farming. The developed coun- 

 tries have the technology to farm 

 their waters efficiently, but they lack 

 the decades of experience that is 

 available in Asia, for example. Aqua- 

 culture in the developed countries 

 must be a profit-making venture, and 

 since markets for many of the species 

 suggested for this are already present, 

 or can be developed with little pro- 

 motion, it would seem that it could 

 indeed be profitable. In the devel- 

 oped countries, too, there has been 

 a boom in oceanic research. A con- 

 siderable share of the results of this 

 scientific research is applicable to 

 mariculture. It is quite obvious that 

 the greatest potential exists for those 

 species that feed low on the food 

 chain, such as some of the crusta- 

 ceans and mollusks. Figure VIII— 11 

 shows one such scheme. 



Biologists who are trying to eval- 

 uate the status and near future po- 

 tential of aquaculture recognize that 

 its maximum effort will be in the 

 near shore waters where there is sub- 

 stantial evidence of extremely high 

 fertility. Of course, the matter of 

 ownership and operating costs be- 

 comes more complicated and costly 

 as the distance from shore increases. 

 In at least one United States oyster- 

 farming operation, radar has been 



used to detect trespassers into leased 

 or owned bottoms who may be help- 

 ing themselves to the ingredients for 

 a stew, from private stock. In Spain, 

 Japan, and the State of Washington, 

 scientists and sea farmers have clearly 

 demonstrated that high oyster pro- 

 duction is possible by using hanging 

 cultures, thereby utilizing all three 

 dimensions of the water. There is 

 no doubt that more use can be made 

 of effluents from electrical power 



plants, especially at the cooler lati- 

 tudes where ponds or tanks using 

 the warm-water effluent from gener- 

 ating stations can greatly lengthen 

 the growing period of fish and shell- 

 fish. 



A number of research projects 

 on mariculture are providing much- 

 needed research results. At the Flor- 

 ida Power and Light Company's new 

 power plant, about forty miles south 



The diagram summarizes a continuous-flow food chain that may be operated in 



various permutations and combinations depending on the desired result. The 



system consists of the following components: 



(1) Diluted (about 10%) sewage effluent as a growth medium for (2) a continuous 

 culture of natural, mixed phytoplankton. which is harvested at the rate of 50% 

 of the culture per day and passed through (3) suspended cultures (strings or 

 racks) of filter-feeding bivalve mollusks (oysters, clams, mussels, or scallops), 

 the phytoplankton diluted with filtered running seawater and so presented 

 to a sufficient number of mollusks that almost all of the suspended algal cells 

 are removed from the water by the animals. (4) Feces and pseudo-feces 

 produced by the mollusks are deposited on the surface of the sand substrate 

 of the animal culture tanks where this material is fed upon by sandworms, 

 bloodworms, and/or other deposit feeders. 



(5) Water flowing through the mollusk compartment containing inorganic and 

 organic nutrients regenerated by the animals is passed into an additional 

 chamber containing macroscopic algae and/or epiphytic, filamentous algae 

 which utilize the regenerated nutrients. (6) The epiphytic algae and asso- 

 ciated microbiota serve as food for browsing animals such as juvenile 

 lobsters, shrimp, mullet, or other suitable animals. 



(7) Although not part of a continuous-flow system, when steady-state equilibrium 

 conditions are reached, animals from any of the above compartments may be 

 fed to carnivores (juvenile striped bass, flounder, and lobsters are examples 

 of readily available species) on a daily-ration basis, the success of this stage 

 being dependent upon the operation of a large enough system to provide 

 a constant supply of food over a sufficiently long period of time to the 

 carnivores. 



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